Add test for ease.

d3.js

@@ -633,7 +633,7 @@ function d3_ease_sin(t) {
 }
 
 function d3_ease_exp(t) {
-  return t ? Math.pow(2, 10 * (t - 1)) - 1e-3 : 0;
+  return Math.pow(2, 10 * (t - 1));
 }
 
 function d3_ease_circle(t) {

src/core/ease.js

@@ -90,7 +90,7 @@ function d3_ease_sin(t) {
 }
 
 function d3_ease_exp(t) {
-  return t ? Math.pow(2, 10 * (t - 1)) - 1e-3 : 0;
+  return Math.pow(2, 10 * (t - 1));
 }
 
 function d3_ease_circle(t) {

test/core/ease-test.js

@@ -0,0 +1,129 @@
+require("../env");
+require("../../d3");
+
+var vows = require("vows"),
+    assert = require("assert");
+
+var suite = vows.describe("d3.ease");
+
+suite.addBatch({
+  "ease": {
+    topic: function() {
+      return d3.ease;
+    },
+    "supports linear easing": function(ease) {
+      var e = ease("linear");
+      assert.inDelta(e(.5), .5, 1e-6);
+    },
+    "supports polynomial easing": function(ease) {
+      var e = ease("poly", 2);
+      assert.inDelta(e(.5), .25, 1e-6);
+    },
+    "supports quadratic easing": function(ease) {
+      var e = ease("quad");
+      assert.inDelta(e(.5), .25, 1e-6);
+    },
+    "supports cubic easing": function(ease) {
+      var e = ease("cubic");
+      assert.inDelta(e(.5), .125, 1e-6);
+    },
+    "supports sinusoidal easing": function(ease) {
+      var e = ease("sin");
+      assert.inDelta(e(.5), 1 - Math.cos(Math.PI / 4), 1e-6);
+    },
+    "supports exponential easing": function(ease) {
+      var e = ease("exp");
+      assert.inDelta(e(.5), 0.03125, 1e-6);
+    },
+    "supports circular easing": function(ease) {
+      var e = ease("circle");
+      assert.inDelta(e(.5), 0.133975, 1e-6);
+    },
+    "supports elastic easing": function(ease) {
+      var e = ease("elastic");
+      assert.inDelta(e(.5), 0.976061, 1e-6);
+    },
+    "supports back easing": function(ease) {
+      var e = ease("back");
+      assert.inDelta(e(.5), -0.0876975, 1e-6);
+    },
+    "supports bounce easing": function(ease) {
+      var e = ease("bounce");
+      assert.inDelta(e(.5), 0.765625, 1e-6);
+    },
+    "all easing functions return approximately 0 for t = 0": function(ease) {
+      assert.inDelta(ease("linear")(0), 0, 1e-9);
+      assert.inDelta(ease("poly", 2)(0), 0, 1e-9);
+      assert.inDelta(ease("quad")(0), 0, 1e-9);
+      assert.inDelta(ease("cubic")(0), 0, 1e-9);
+      assert.inDelta(ease("sin")(0), 0, 1e-9);
+      assert.inDelta(ease("exp")(0), 0, 1e-3); // XXX
+      assert.inDelta(ease("circle")(0), 0, 1e-9);
+      assert.inDelta(ease("elastic")(0), 0, 1e-9);
+      assert.inDelta(ease("back")(0), 0, 1e-9);
+      assert.inDelta(ease("bounce")(0), 0, 1e-9);
+    },
+    "all easing functions return approximately 1 for t = 1": function(ease) {
+      assert.inDelta(ease("linear")(1), 1, 1e-9);
+      assert.inDelta(ease("poly", 2)(1), 1, 1e-9);
+      assert.inDelta(ease("quad")(1), 1, 1e-9);
+      assert.inDelta(ease("cubic")(1), 1, 1e-9);
+      assert.inDelta(ease("sin")(1), 1, 1e-9);
+      assert.inDelta(ease("exp")(1), 1, 1e-9);
+      assert.inDelta(ease("circle")(1), 1, 1e-9);
+      assert.inDelta(ease("elastic")(1), 1, 1e-3); // XXX
+      assert.inDelta(ease("back")(1), 1, 1e-9);
+      assert.inDelta(ease("bounce")(1), 1, 1e-9);
+    },
+    "the -in suffix returns the identity": function(ease) {
+      assert.equal(ease("linear-in"), ease("linear"));
+      assert.equal(ease("quad-in"), ease("quad"));
+    },
+    "the -out suffix returns the reverse": function(ease) {
+      assert.inDelta(ease("sin-out")(.25), 1 - ease("sin-in")(.75), 1e-6);
+      assert.inDelta(ease("bounce-out")(.25), 1 - ease("bounce-in")(.75), 1e-6);
+      assert.inDelta(ease("elastic-out")(.25), 1 - ease("elastic-in")(.75), 1e-6);
+    },
+    "the -in-out suffix returns the reflection": function(ease) {
+      assert.inDelta(ease("sin-in-out")(.25), .5 * ease("sin-in")(.5), 1e-6);
+      assert.inDelta(ease("bounce-in-out")(.25), .5 * ease("bounce-in")(.5), 1e-6);
+      assert.inDelta(ease("elastic-in-out")(.25), .5 * ease("elastic-in")(.5), 1e-6);
+    },
+    "the -out-in suffix returns the reverse reflection": function(ease) {
+      assert.inDelta(ease("sin-out-in")(.25), .5 * ease("sin-out")(.5), 1e-6);
+      assert.inDelta(ease("bounce-out-in")(.25), .5 * ease("bounce-out")(.5), 1e-6);
+      assert.inDelta(ease("elastic-out-in")(.25), .5 * ease("elastic-out")(.5), 1e-6);
+    },
+    "does not clamp input time": function(ease) {
+      var e = ease("linear");
+      assert.inDelta(e(-1), -1, 1e-6);
+      assert.inDelta(e(2), 2, 1e-6);
+    },
+    "poly": {
+      "supports an optional polynomial": function(ease) {
+        var e = ease("poly", 1);
+        assert.inDelta(e(.5), .5, 1e-6);
+        var e = ease("poly", .5);
+        assert.inDelta(e(.5), Math.SQRT1_2, 1e-6);
+      }
+    },
+    "elastic": {
+      "supports an optional amplifier (>1)": function(ease) {
+        var e = ease("elastic", 1.5);
+        assert.inDelta(e(.5), 0.998519, 1e-6);
+      },
+      "supports an optional amplifier (>1) and period (>0)": function(ease) {
+        var e = ease("elastic", 1.5, .5);
+        assert.inDelta(e(.5), 0.96875, 1e-6);
+      }
+    },
+    "back": {
+      "supports an optional speed": function(ease) {
+        var e = ease("back", 2);
+        assert.inDelta(e(.5), -0.125, 1e-6);
+      }
+    }
+  }
+});
+
+suite.export(module);